FIGURE 4.

Daxx inhibits the p300-enhanced C/EBPβ-dependent transcription. A, QT6 cells were transfected with the indicated combinations of expression vectors for FLAG-C/EBPβ (1 μg), HA-p300 (5 μg), and HA-Daxx (5 μg) together with the C/EBPβ-responsive p240-Luc reporter construct (3 μg) and pCMVβ (0.5 μg). Cells were harvested after 24 h, and luciferase and β-galactosidase activities were determined. The columns show the average luciferase activity normalized to the β-galactosidase activity. Thin lines show standard deviations. Data presented are derived from at least four independent experiments. The β-galactosidase-normalized luciferase activity mediated by exclusive expression of FLAG-C/EBPβ was arbitrarily set as one. B, Northern blot analysis of polyadenylated RNA from QT6 cells transfected with pCMVβ (0.5 μg) and the indicated combinations of FLAG-C/EBPβ (0.75 μg), HA-p300 (5 μg), and HA-Daxx (2 and 5 μg) expression vectors. β-Galactosidase assays of aliquots of the cells were used to confirm similar the transfection efficiencies in each case. The blot was hybridized sequentially with probes specific for the chicken MRP126 gene and the ribosomal protein S17 gene which was used as internal control.